About five years ago, the Click-to-Open Rate (CTOR) was a hot topic, heralded as the best way to understand the effectiveness of email content, but the sizzle began to fizzle very quickly. With only Dynamic Content 1.0 being used, and some challenges with interpreting the meaning of CTOR results, attention to the metric cooled off within a year (though of course you can still easily check it in your ESP dashboard).
Back then, CTOR was also referred to by some as the Effective Rate. Hal Licino spoke about how the effective rate “provides significant insight into how your loyalty-based and retention processes are being received by your audience.”
The value of CTOR was heavily debated at that time; in particular, there were mathematical concerns about the dependency of the value on open rate. Many think that the value of open rate is significantly undermined by the way images are rendered, or not rendered. In the end, skeptics like Derek Harding, the Managing Director of J-Labs, left the discussion with this dismissive note:
“My cynical side suspects that since the divisor for CTOR is smaller than that for CTR it's being adopted by some because it's like CTR but bigger.”
Regardless, the CTOR — unique clicks divided by unique opens, multiplied by 100 — can provide you with a much more relevant and informative approach to how well your content is performing. Alternatively, according to Loren McDonald at Silverpop, the CTOR “measures how effectively the content, design, and offers in your message are driving recipient clicks.”
So, why CTOR and not the more obvious metrics like delivery rate, open rate, click-through rate, or conversion rate? What you measure depends on what information you want to uncover.
Open Rate
The open rate is a good measure of how effective your subject lines are, how much your list members trust you, and how much you have captured the ideal sending frequency. It’s also a good indication of how well you are bypassing spam filters. But it can be problematic, such as when email clients block images in an opened email; unless those images are downloaded, it doesn’t register as having been opened.
Open Rate (OR) is calculated as follows:
% Open Rate = # email opens / # emails sent (or sometimes: # emails delivered) x 100
Click-Through Rate
Secondly, the click-through rate is a good measure of how effective your overall content, layout, and links are. When CTR is high, it means your overall content is engaging, your calls to action are clear, and your list members are loyal. It’s influenced by the health of your email list, deliverability factors, and how relevant your content is or isn’t. However, a lower CTR can be influenced by the health of your email list, deliverability factors, and other factors.
Click-Through Rate (CTR) is calculated as follows:
% CTR = # of clicks in an email / # of emails sent x 100
Both of these metrics are very important, and you should be paying attention to them. However, they fall short when it comes to what you should be paying attention to with Dynamic Content 2.0.
Neither open rate nor CTR tell you about the engagement level of your audience or the true quality of your different types of content. You can get some indication and use your gut to figure out the rest, but if you truly want to be an email marketer who is focused on conversion optimization, you need to know more.
You need a metric that zeros in on the relevance of the message and the effectiveness of each block that contains an offer, product, or article. You’ll also want to understand the effectiveness of the number and location of links, and — especially with dynamic content such as social proof — the level of trust that recipients place in your brand.
Click-to-Open Rate
The Click-to-Open Rate (CTOR) has a lot to say. Since it only measures subscribers who have taken some action with your campaign — they have at least opened the message — it’s useful for understanding how subscribers interact with your content.
To calculate CTOR at a campaign level, you can use this formula:
% CTOR = # of clicks in an email / # of opens x 100
For example, if your Open Rate is 5028, and your CTR is 733, the CTOR formula looks like this:
14.5% (733 / 5028 = 0.145 x 100 = 14.5)
For Dynamic Content 2.0, we have demonstrated that CTOR is the best measure, but that it should be applied on an individual content piece level, and not only to the overall campaign.
The classic CTOR formula for an entire campaign is therefore modified to the new CTOR for campaigns with dynamic areas:
% CTOR = # of clicks on the dynamic content block / # of opens for emails containing that specific block x 100
